Wireless base station apparatus and system to avoid preamble interference

ABSTRACT

A radio base-station apparatus with improved frame transmission efficiency by avoiding interference of preambles and frame control information between sectors of a cell or between cells with a frequency reuse factor. In the apparatus OFDMA multiple-access processing is performed for each of a plurality of sectors of a cell, and frames made of logical subchannel numbers and OFDMA symbol numbers are configured in synchronization respectively for the plurality of sectors, and offsets are added to the beginnings of given frames such that the preambles and frame control information arranged sequentially from the beginnings of the frames do not overlap on the OFDMA symbol numbers.

TECHNICAL FIELD

The present invention relates to a radio base-station apparatus using an OFDMA system, and particularly to a radio base-station apparatus that is capable of avoiding interference between sectors when a plurality of sectors in a cell are used with frequency reuse factor 1.

BACKGROUND ART

IEEE 802.16 was established as a standard for radio MAN (Metropolitan Area Network), initially for FWA (Fixed Wireless Access) use, and it originally supports techniques for realizing high-efficiency radio transmission through high-level optimization of base stations, such as QoS (Quality of Service), AAS (Adaptive Antenna System), transmission diversity, etc.

Recently, schemes with excellent frequency-selective fading tolerance have been added thereto, such as OFDM (Orthogonal Frequency Division Multiplexing) and OFDMA (Orthogonal Frequency Division Multiple Access), and it now deals with radio access communications in multipath environments unanticipatedly.

With this situation, in mobile communications, expansions are now in progress mainly with OFDMA that offers subchannelization of individual terminal stations and is capable of handling propagation environments varying independently among the terminal stations.

Now, a conventional OFDMA technique will be described.

FIGS. 13 to 15 show a technique described in the IEEE 802.16 (IEEE P802.16-REVd/D5-2004, downloaded on 2004.11.8), for example, where FIG. 13 illustrates a sector configuration in which one cell is divided into three sectors, FIG. 14 illustrates the configuration of a radio base-station apparatus divided into segments corresponding to individual sectors, and FIG. 15 illustrates the OFDMA frame structure.

In FIG. 13, a cell 100 is divided into three sectors 101 a, 101 b and 101 c. The cell 100 has a radio base-station apparatus 103 having antennas 102 a, 102 b and 102 c for sending and receiving radio signals to and from terminal stations (not shown) located in the areas of the sectors 101 a, 101 b and 101 c.

In FIG. 14, the radio base-station apparatus 103 includes PHY (physical layer) processing blocks 104 a, 104 b and 104 c for performing OFDMA modulation/demodulation and frame formation respectively for the sectors 101 a, 101 b and 101 c, radio transmitter/receiver blocks 105 a, 105 b and 105 c for sending and receiving radio signals through the antennas 102 a, 102 b and 102 c to and from terminal stations not shown, a MAC (Media Access Control) processing block 106 for performing data allocation to the individual segments corresponding to the sectors 101 a, 101 b and 101 c, and a network I/F 107 connected to the MAC processing block 106 through a network or the like not shown.

In FIG. 15, the vertical axis shows the entire band of radio frequencies used with logical subchannel numbers 110, and the horizontal axis shows time with OFDMA symbol numbers 111. The logical subchannel numbers 110 are divided into three segments in correspondence with the sectors 101 a, 101 b and 101 c. The logical subchannel numbers 110 and OFDMA symbol numbers 111 thus form frames 112 a, 112 b and 112 c for individual sectors 101 a, 101 b and 101 c, which respectively include, sequentially from the beginning, preambles 113 a, 113 b and 113 c, broadcast information 114 a, 114 b and 114 c, downlink allocation information 115 a, 115 b and 115 c, uplink allocation information 116 a, 116 b and 116 c, downlink data regions 117 a, 117 b and 117 c, and uplink data regions 118 a, 118 b and 118 c. The broadcast information 114 a, 114 b and 114 c, downlink allocation information 115 a, 115 b and 115 c, and uplink allocation information 116 a, 116 b and 116 c form frame control information.

Next, its operation will be described referring to FIGS. 13 to 15.

The MAC processing block 106 performs segmentation processing by dividing the entire radio frequency band for the logical subchannel numbers 110 into three segments corresponding to the sectors 101 a, 101 b and 101 c, and allocating data to the individual segments.

Next, with the three segments corresponding to the sectors 101 a, 101 b and 101 c, the PHY processing blocks 104 a, 104 b and 104 c respectively generate the frames 112 a, 112 b and 112 c and perform OFDMA modulation/demodulation processing, with the frames 112 a, 112 b and 112 c respectively including, sequentially from the beginning, the preambles 113 a, 113 b and 113 c, the broadcast information 114 a, 114 b and 114 c, the downlink allocation information 115 a, 115 b and 115 c, the uplink allocation information 116 a, 116 b and 116 c, the downlink data regions 117 a, 117 b and 117 c, and the uplink data regions 118 a, 118 b and 118 c.

Then, the radio transmitter/receiver blocks 105 a, 105 b and 105 c perform frequency conversion and amplification processing to enable radio-signal transmission/reception with terminal stations, and radio signals are transmitted to and received from terminal stations through the antennas 102 a, 102 b and 102 c.

Non-Patent Document 1: IEEE P802.16-REVd/D5-2004, downloaded on 2004.11.8.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

With the conventional radio base-station apparatus described above, the entire band of radio frequencies used is divided into three segments corresponding to the sectors 101 a, 101 b and 101 c, and therefore the maximum radio-signal transmission rate is reduced to ⅓ or below as compared with frequency reuse factor 1 in which the entire band of same radio frequencies is allocated to each of the sectors 101 a, 101 b and 101 c, for example.

In order to avoid the reduction of maximum transmission rate, when the subchannelization function of OFDMA is used with the frequency reuse factor 1 in which the same entire radio frequency band is allocated to each of the sectors 101 a, 101 b and 101 c, then interference occurs between the preambles 113 a, 113 b and 113 c, broadcast information 114 a, 114 b and 114 c, downlink allocation information 115 a, 115 b and 115 c, and uplink allocation information 116 a, 116 b and 116 c, resulting in reduced transmission efficiency.

The same problem occurs also when the frequency reuse factor 1, which allocates the entire same radio frequency band, is applied to another cell adjacent to the cell 100, for example.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a radio base-station apparatus configured to work with frequency reuse factor 1 to avoid reduction of maximum transmission rate, and to achieve improved frame transmission efficiency by avoiding interference of preambles and frame control information, including broadcast information, downlink allocation information and uplink allocation information, between sectors in a cell and between adjacent cells when frequency reuse factor 1 is adopted.

Means for Solving the Problems

According to the present invention, a radio base-station apparatus is configured to work with a frequency reuse factor 1 where a plurality of sectors of a cell are used with a same radio frequency, and the radio base-station apparatus performs OFDMA multiple-access processing for each of the plurality of sectors, and configures frames respectively for the plurality of sectors with logical subchannel numbers and OFDMA symbol numbers such that preambles and pieces of frame control information arranged sequentially from the beginnings of the frames do not interfere with each other between the frames formed respectively for the plurality of sectors.

EFFECTS OF THE INVENTION

According to the radio communications base-station apparatus of the present invention, the frames respectively for the plurality of sectors are configured such that preambles and frame control information pieces arranged sequentially from the beginnings of the frames do not interfere with each other between the frames respectively corresponding to the plurality of sectors, and thus no interference occurs among the preambles and frame control information pieces arranged in the individual frames, and the frame transmission efficiency is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] A diagram illustrating a sector configuration according to a first preferred embodiment of the present invention.

[FIG. 2] A diagram illustrating a radio communications base-station apparatus of the first preferred embodiment of the present invention.

[FIG. 3] A diagram illustrating the frame structure of the first preferred embodiment of the present invention.

[FIG. 4] A diagram illustrating the frame structure according to a second preferred embodiment of the present invention.

[FIG. 5] A diagram illustrating the frame structure according to a third preferred embodiment of the present invention.

[FIG. 6] A diagram illustrating a radio communications base-station apparatus according to a fourth preferred embodiment of the present invention.

[FIG. 7] A diagram illustrating a sector configuration of the fourth preferred embodiment of the present invention.

[FIG. 8] A diagram illustrating a cell configuration according to a fifth preferred embodiment of the present invention.

[FIG. 9] A diagram illustrating the frame structure of the fifth preferred embodiment of the present invention.

[FIG. 10] A diagram illustrating the frame structure according to a sixth preferred embodiment of the present invention.

[FIG. 11] A diagram illustrating the frame structure according to a seventh preferred embodiment of the present invention.

[FIG. 12] A diagram illustrating a network configuration according to an eighth preferred embodiment of the present invention.

[FIG. 13] A diagram illustrating a conventional sector configuration.

[FIG. 14] A diagram illustrating a conventional radio communications base-station apparatus.

[FIG. 15] A diagram illustrating a conventional frame structure.

DESCRIPTION OF REFERENCE CHARACTERS

1 Cell; 2 a, 2 b, 2 c Sectors; 3, 3 a, 3 b, 3 c Radio base-station apparatus (devices);

4 a, 4 b, 4 c Antennas; 5 a, 5 b, 5 c Network I/F;

6 a, 6 b, 6 c MAC processing blocks; 7 a, 7 b, 7 c PHY processing blocks;

8 a, 8 b, 8 c Radio transmitter/receiver blocks; 9 Reference clock source; 9 a Reference clock signal;

10 System clock generator; 10 a System clock signal;

10 b Frame start signal; 11, 12 Delay adders;

11 a, 12 a Frame start signals;

13 a, 13 b, 13 c Logical subchannel numbers;

14 OFDMA symbol numbers; 15 a, 15 b, 15 c Frames;

16 a, 16 b, 16 c Preambles; 17 a, 17 b, 17 c Broadcast information;

18 a, 18 b, 18 c Downlink allocation information;

19 a, 19 b, 19 c Uplink allocation information;

20 a, 20 b, 20 c Downlink data regions;

21 a, 21 b, 21 c Uplink data regions; and

22 a, 22 b NULL subcarrier regions.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, in order to more fully describe the present invention, the best mode for carrying out the invention will be described referring to the accompanying drawings.

First Preferred Embodiment

A radio base-station apparatus according to a first preferred embodiment of the present invention will be described referring to FIGS. 1 to 3.

FIG. 1 is a diagram illustrating a sector configuration in which one cell as a communication area of one radio base-station apparatus is divided into three sectors.

In FIG. 1, a cell 1 is divided into three sectors 2 a, 2 b and 2 c, and the entire band of the same radio frequencies is allocated to each (so-called frequency reuse factor 1). The cell 1 has a radio base-station apparatus 3. The radio base-station apparatus 3 includes radio base-station devices 3 a, 3 b and 3 c respectively corresponding to the sectors 2 a, 2 b and 2 c. The radio base-station devices 3 a, 3 b and 3 c respectively have antennas 4 a, 4 b and 4 c for transmitting and receiving radio signals to and from terminal stations (not shown) located in the areas of the sectors 2 a, 2 b and 2 c.

FIG. 2 is a diagram illustrating the configuration of the radio base-station apparatus.

In FIG. 2, the radio base-station device 3 a works as a master for the radio base-station devices 3 b and 3 c. The radio base-station device 3 a includes a network I/F 5 a connected to a network not shown, a MAC processing block 6 a for performing data allocation for the sector 2 a, a PHY processing block 7 a for performing frame formation and OFDMA modulation/demodulation processing for the sector 2 a, a radio transmitter/receiver block 8 a for transmitting and receiving radio signals through the antenna 4 a to and from terminal stations (not shown) located in the area of the sector 2 a, a reference clock source 9 for outputting a reference clock signal 9 a, and a system clock generator 10 for applying frequency conversion etc. to the reference clock signal 9 a to generate and output a given system clock signal 10 a and frame start signal 10 b.

The radio base-station device 3 b works as a slave for the radio base-station device 3 a as a master. The radio base-station device 3 b includes a network I/F 5 b connected to the network not shown, a MAC processing block 6 b for performing data allocation for the sector 2 b, a PHY processing block 7 b for performing frame formation and OFDMA modulation/demodulation processing for the sector 2 b, a radio transmitter/receiver block 8 b for transmitting and receiving radio signals through the antenna 4 b to and from terminal stations (not shown) located in the area of the sector 2 b, and a delay adder 11 for adding a given offset, for the sector 2 b, to the frame start signal 10 b to output a frame start signal 11 a.

The radio base-station device 3 c works as a slave for the radio base-station device 3 a as a master. The radio base-station device 3 c includes a network I/F 5 c connected to the network not shown, a MAC processing block 6 c for performing data allocation for the sector 2 c, a PHY processing block 7 c for performing frame formation and OFDMA modulation/demodulation processing for the sector 2 c, a radio transmitter/receiver block 8 c for transmitting and receiving radio signals through the antenna 4 c to and from terminal stations (not shown) located in the area of the sector 2 c, and a delay adder 12 for adding a given offset, for the sector 2 c, to the frame start signal 10 b to output a frame start signal 12 a.

FIG. 3 is a diagram illustrating the OFDMA frame structure.

In FIG. 3, the vertical axis shows frequency, which is represented as logical subchannel numbers 13 a, 13 b and 13 c where the entire band of same radio frequencies is allocated to each of the three sectors 2 a, 2 b and 2 c. This configures a frequency reuse factor 1 in which the entire same radio frequency band is allocated to each of the sectors 2 a, 2 b and 2 c. The horizontal axis shows time, which is represented as OFDMA symbol numbers 14.

Thus, the logical subchannel numbers 13 a, 13 b, and 13 c corresponding to the sectors 2 a, 2 b and 2 c and the OFDMA symbol numbers 14 configure frames 15 a, 15 b and 15 c as units for transmission and reception of radio signals.

The frames 15 a, 15 b and 15 c respectively include preambles 16 a, 16 b and 16 c, broadcast information 17 a, 17 b and 17 c, downlink allocation information 18 a, 18 b and 18 c, uplink allocation information 19 a, 19 b and 19 c, downlink data regions 20 a, 20 b and 20 c, and uplink data regions 21 a, 21 b and 21 c, which are sequentially arranged from the beginning of each frame. The broadcast information 17 a, 17 b and 17 c, downlink allocation information 18 a, 18 b and 18 c, and uplink allocation information 19 a, 19 b and 19 c form frame control information.

In the frames 15 a and 15 b, NULL subcarrier regions 22 a and 22 b with no output of subcarriers, including pilot subcarriers, immediately precede the downlink data regions 20 a and 20 b, respectively.

Next, its operation will be described referring to FIGS. 1 to 3.

First, the reference clock source 9 of the radio base-station device 3 a for the sector 2 a outputs a reference clock 9 a.

By using the reference clock 9 a, the radio transmitter/receiver blocks 8 a, 8 b and 8 c synchronize the carriers for transmission and reception by the radio base-station devices 3 a, 3 b and 3 c.

Also, the reference clock 9 a is inputted to the system clock generator 10, and the system clock generator 10 applies frequency conversion etc. to it so as to generate and output a given system clock signal 10 a and frame start signal 10 b as reference.

Then, by using the system clock signal 10 a and referring to the frame start signal 10 b, the PHY processing block 7 a of the radio base-station device 3 a for the sector 2 a forms the frame 15 a, as shown in FIG. 3, sequentially including the preamble 16 a, broadcast information 17 a, downlink allocation information 18 a, uplink allocation information 19 a, NULL subcarrier region 22 a, downlink data region 20 a, and uplink data region 21 a.

In the radio base-station device 3 b for the sector 2 b, the delay adder 11 adds a given amount of delay to the frame start signal 10 b to generate a frame start signal 11 a so that the beginning of the frame 15 b will not overlap on the OFDMA symbol numbers 14 with the preamble 16 a of the frame 15 a, its broadcast information 17 a, downlink allocation information 18 a, and uplink allocation information 19 a. Then, by using the system clock signal 10 a and referring to the frame start signal 11 a, the PHY processing block 7 b of the radio base-station device 3 b forms the frame 15 b, as shown in FIG. 3, sequentially including the preamble 16 b, broadcast information 17 b, downlink allocation information 18 b, uplink allocation information 19 b, NULL subcarrier region 22 b, downlink data region 20 b, and uplink data region 21 b.

In the radio base-station device 3 c for the sector 2 c, the delay adder 12 adds a given amount of delay to the frame start signal 10 b to generate a frame start signal 12 a so that the beginning of the frame 15 c will not overlap on the OFDMA symbol numbers 14 with the preamble 16 a of the frame 15 a, its broadcast information 17 a, downlink allocation information 18 a, and uplink allocation information 19 a, and with the preamble 16 b of the frame 15 b, its broadcast information 17 b, downlink allocation information 18 b, and uplink allocation information 19 b. Then, by using the system clock signal 10 a and referring to the frame start signal 12 a, the PHY processing block 7 c of the radio base-station device 3 c forms the frame 15 c, as shown in FIG. 3, sequentially including the preamble 16 c, broadcast information 17 c, downlink allocation information 18 c, uplink allocation information 19 c, downlink data region 20 c, and uplink data region 21 c.

By configuring the frames 15 a, 15 b and 15 c in this way, no overlap occurs on the OFDMA symbol numbers 14 between the preambles 16 a, 16 b and 16 c of the respective frames 15 a, 15 b and 15 c, their respective broadcast information 17 a, 17 b and 17 c, downlink allocation information 18 a, 18 b and 18 c, and uplink allocation information 19 a, 19 b and 19 c. Thus, when the radio base-station devices 3 a, 3 b and 3 c transmit/receive radio signals to/from terminal stations, interference does not occur between the preambles 16 a, 16 b and 16 c, broadcast information 17 a, 17 b and 17 c, downlink allocation information 18 a, 18 b and 18 c, and uplink allocation information 19 a, 19 b and 19 c, which provides improved frame transmission efficiency.

Then, by using the timings of the frames 15 a, 15 b and 15 c, radio signals are transmitted and received to and from the terminal stations located in the sectors 2 a, 2 b and 2 c, through the radio transmitter/receiver blocks 8 a, 8 b and 8 c and the antennas 4 a, 4 b and 4 c of the radio base-station devices 3 a, 3 b and 3 c corresponding to the sectors 2 a, 2 b and 2 c.

Second Preferred Embodiment

In the first preferred embodiment, the preambles 16 a, 16 b and 16 c of the frames 15 a, 15 b and 15 c corresponding to the sectors 2 a, 2 b and 2 c do not overlap each other on the OFDMA symbol numbers 14; however, as shown with the OFDMA frame structure illustrated in FIG. 4, the preambles of the frames 15 a, 15 b and 15 c may be made of different patterns of preambles 24 a, 24 b and 24 c that have no correlation with each other, i.e. that can be detected even when interference occurs between preambles, and then they may coincide with each other on the OFDMA symbol numbers 14. The reference characters 25 a, 25 b, 25 c and 25 d indicate NULL subcarrier regions. In this case, the delay adders 11 and 12 add no offsets. In FIG. 4, the same reference characters as those shown in the first preferred embodiment indicate the same or corresponding components, and so they are not described again here.

In this way, the preambles 24 a, 24 b and 24 c having different patterns with no correlation with each other overlap each other on the OFDMA symbol numbers 14, and thus the overhead is reduced for the time of the overlap of preambles 24 a 24 b and 24 c, and the frame transmission efficiency is further improved than in the first preferred embodiment.

Third Preferred Embodiment

In the second preferred embodiment, the preambles 24 a, 24 b and 24 c of the frames 15 a, 15 b and 15 c corresponding to the sectors 2 a, 2 b and 2 c overlap each other on the OFDMA symbol numbers 14; however, as shown with the OFDMA frame structure illustrated in FIG. 5, the frame control information, or the broadcast information 26 a, 26 b and 26 c, downlink allocation information 27 a, 27 b and 27 c, and uplink allocation information 28 a, 28 b and 28 c, may be arranged such that they do not overlap on the logical subchannel numbers 13 a, 13 b and 13 c. The reference characters 29 a, 29 b, 29 c and 29 d indicate NULL subcarrier regions. In this case, the delay adders 11 and 12 add no offsets. In FIG. 5, the same reference characters as those shown in the first and second preferred embodiments indicate the same or corresponding components and so they are not described again here.

In this way, the frame control information, or the broadcast information 26 a, 26 b and 26 c, downlink allocation information 27 a, 27 b and 27 c, and uplink allocation information 28 a, 28 b and 28 c, can overlap on the OFDMA symbol numbers 14, and thus the overhead is reduced for the time of the overlap of broadcast information 26 a, 26 b and 26 c, downlink allocation information 27 a, 27 b and 27 c, and uplink allocation information 28 a, 28 b and 28 c, and the frame transmission efficiency is further improved than in the second preferred embodiment.

Fourth Preferred Embodiment

In the first to third preferred embodiments, as shown in FIG. 2, the radio base-station device 3 a includes the reference clock source 9 that outputs the reference clock signal 9 a, but, as shown by the configuration of a radio base-station apparatus illustrated in FIG. 6 and the sector configuration illustrated in FIG. 7, the reference clock source 9 may be replaced by a GPS receiver 32 that extracts a reference clock signal 9 a from a GPS signal received through an antenna 31 from a GPS satellite not shown. In FIGS. 6 and 7, the same reference characters as those used in the first to third preferred embodiments indicate the same or corresponding components and so they are not described again here.

With this configuration, the GPS receiver 32 extracts the reference clock signal 9 a from the GPS signal received through the antenna 31 from a GPS satellite not shown. In other respects, the operation is the same as those of the first to third preferred embodiments.

The first to fourth preferred embodiments have shown a configuration in which one cell is divided into three sectors, but this configuration is only illustrative and not restrictive, and not intended to particularly limit the number of sectors.

Fifth Preferred Embodiment

In the fourth preferred embodiment, the reference clock signal is extracted from a GPS signal received from a GPS satellite, and then, in a radio communications system having a plurality of cells, it is easy to synchronize operations as described in the first to third preferred embodiments among the plurality of cells.

FIGS. 8 and 9 illustrate a radio communications system having a plurality of cells according to a fifth preferred embodiment of the present invention.

FIG. 8 illustrates a sector configuration that has three cells each configured as shown in the fourth preferred embodiment, and each cell is divided into three sectors.

FIG. 9 is a diagram illustrating the OFDMA frame structure for the individual sectors shown in FIG. 8. In FIGS. 8 and 9, the same reference characters as those used in the first to fourth preferred embodiments indicate the same or corresponding components, and so they are not described gain here.

In FIG. 8, the cell 1 corresponds to that shown in FIG. 7 of the fourth preferred embodiment. Cells 35 and 36 are provided adjacent to the cell 1.

Like the cell 1, the cell 35 is divided into three sectors 37 a, 37 b and 37 c, and each is assigned the same entire radio frequency band as that assigned to the sectors 2 a, 2 b and 2 c of the cell 1 (so-called frequency reuse factor 1). The cell 35 has a radio base-station apparatus 38. The radio base-station apparatus 38 includes radio base-station devices 38 a, 38 b and 38 c respectively corresponding to the sectors 37 a, 37 b and 37 c. The radio base-station devices 38 a, 38 b and 38 c respectively have antennas 39 a, 39 b and 39 c for transmitting and receiving radio signals to and from terminal stations (not shown) located in the areas of the sectors 37 a, 37 b and 37 c. The radio base-station device 38 a serving as a master has an antenna 40 for receiving a GPS signal from a GPS satellite not shown. The radio base-station devices 38 a, 38 b and 38 c are configured in correspondence respectively with the radio base-station devices 3 a, 3 b and 3 c shown in FIG. 6 in the fourth preferred embodiment.

Also, like the cell 1, the cell 36 is divided into three sectors 41 a, 41 b and 41 c, and each is assigned the same entire radio frequency band as that assigned to the sectors 2 a, 2 b and 2 c of the cell 1 (so-called frequency reuse factor 1). The cell 36 has a radio base-station apparatus 42. The radio base-station apparatus 42 includes radio base-station devices 42 a, 42 b and 42 c respectively corresponding to the sectors 41 a, 41 b and 41 c. The radio base-station devices 42 a, 42 b and 42 c respectively have antennas 43 a, 43 b and 43 c for transmitting and receiving radio signals to and from terminal stations (not shown) located in the areas of the sectors 41 a, 41 b and 41 c. The radio base-station device 42 a serving as a master has an antenna 44 for receiving a GPS signal from a GPS satellite not shown. The radio base-station devices 42 a, 42 b and 42 c are configured in correspondence respectively with the radio base-station devices 3 a, 3 b and 3 c shown in FIG. 6 in the fourth preferred embodiment.

In FIG. 9, the vertical axis shows frequency, and the entire band of same radio frequencies is allocated to each of the three sectors 2 a, 2 b, 2 c of the cell 1, the three sectors 37 a, 37 b and 37 c of the cell 35, and the three sectors 41 a, 41 b and 41 c of the cell 36. This allocation is represented with logical subchannel numbers 13 a, 13 b and 13 c for the sectors 2 a, 2 b and 2 c, logical subchannel numbers 45 a, 45 b and 45 c for the sectors 37 a, 37 b and 37 c, and logical subchannel numbers 46 a, 46 b and 46 c for the sectors 41 a, 41 b and 41 c. This configures a frequency reuse factor 1 in which the entire same radio frequency band is allocated to each of the sectors 2 a, 2 b, 2 c, 37 a, 37 b, 37 c, 41 a, 41 b and 41 c. The horizontal axis shows time, represented as OFDMA symbol numbers 14.

Thus, the logical subchannel numbers 13 a, 13 b, 13 c, 45 a, 45 b, 45 c, 46 a, 46 b and 46 c for the sectors 2 a, 2 b, 2 c, 37 a, 37 b, 37 c, 41 a, 41 b and 41 c and the OFDMA symbol numbers 14 form frames 47 a, 47 b and 47 c as units for transmission and reception of radio signals. In this case, the frame 47 a corresponds to the sectors 2 a, 37 a and 41 a, the frame 47 b corresponds to the sectors 2 b, 37 b and 41 b, and the frame 47 c corresponds to the sectors 2 c, 37 c and 41 c.

The frame 47 a corresponds to the sectors 2 a, 37 a and 41 a of the cells 1, 35 and 36, which includes, sequentially from the beginning, preambles 16 a, 47 a and 48 a, frame control information 49 a, 50 a and 51 a, NULL subcarrier regions 22 a, 52 a and 53 a, downlink data regions 20 a, 54 a and 55 a, and uplink data regions 21 a, 56 a and 57 a.

The frame 47 b corresponds to the sectors 2 b, 37 b and 41 b of the cells 1, 35 and 36, which includes, sequentially from the beginning, preambles 16 b, 47 b and 48 b, frame control information 49 b, 50 b and 51 b, NULL subcarrier regions 22 b, 52 b and 53 b, downlink data regions 20 b, 54 b and 55 b, and uplink data regions 21 b, 56 b and 57 b.

The frame 47 c corresponds to the sectors 2 c, 37 c and 41 c of the cells 1, 35 and 36, which includes, sequentially from the beginning, preambles 16 c, 47 c and 48 c, frame control information 49 c, 50 c and 51 c, downlink data regions 20 c, 54 c and 55 c, and uplink data regions 21 c, 56 c and 57 c.

The frame control information includes broadcast information, downlink allocation information, and uplink allocation information. For example, the frame control information 49 a includes the broadcast information 17 a, the downlink allocation information 18 a, and the uplink allocation information 19 a shown in FIG. 3.

Next, its operation will be described referring to FIGS. 6, 8 and 9.

The operations of the frames 47 a, 47 b and 47 c that correspond to the sectors 2 a, 2 b and 2 c of the cell 1 are the same as those described in the first and fourth preferred embodiments. The frames 47 a, 47 b and 47 c provided for the sectors 2 a, 2 b and 2 c correspond to the frames 15 a, 15 b and 15 c described in the first and fourth preferred embodiments.

This preferred embodiment differs from the first and fourth preferred embodiments in that a plurality of cells perform the operation as described in the first and fourth preferred embodiments.

In the sectors 2 a, 37 a and 41 a of the cells 1, 35 and 36, the radio base-station devices 3 a, 38 a and 42 a as masters receive the same GPS signal through the antennas 32, 40 and 44 from a GPS satellite not shown.

First, when the radio base-station device 3 a, provided for the sector 2 a of the cell 1 and serving as a master, receives the GPS signal through the antenna 32, then the GPS receiver 32 extracts the reference clock 9 a as described in the fourth preferred embodiment. This reference clock 9 a is inputted to the system clock generator 10. Then, as described in the first preferred embodiment, in the radio base-station devices 3 b and 3 c provided for the sectors 2 b and 2 c and serving as slaves, given offsets are added to the frame start signal 10 b outputted from the system clock generator 10, and the frames 47 a, 47 b and 47 c are configured such that, as shown with the cell 1 in FIG. 9, no overlap occurs on the OFDMA symbol numbers 14 among the preamble 16 a and frame control information 49 a for the sector 2 a, the preamble 16 b and frame control information 49 b for the sector 2 b, and the preamble 16 c and frame control information 49 c for the sector 2 c.

Also, when the radio base-station device 38 a, provided for the sector 37 a of the cell 35 and serving as a master, receives the GPS signal through the antenna 40, then the radio base-station device 38 a as the master and the radio base-station devices 38 b and 38 c as slaves operate in the same way as the radio base-station devices 3 a, 3 b and 3 c. Then, as shown with the cell 35 in FIG. 9, the frames 47 a, 47 b and 47 c are configured such that no overlap occurs on the OFDMA symbol numbers 14 among the preamble 47 a and frame control information 50 a for the sector 37 a, the preamble 47 b and frame control information 50 b for the sector 37 b, and the preamble 47 c and frame control information 50 c for the sector 37 c.

Also, when the radio base-station device 42 a, provided for the sector 41 a of the cell 36 and serving as a master, receives the GPS signal through the antenna 44, then the radio base-station device 42 a as the master and the radio base-station devices 42 b and 42 c as slaves operate in the same way as the radio base-station devices 3 a, 3 b and 3 c. Then, as shown with the cell 36 in FIG. 9, the frames 47 a, 47 b and 47 c are configured such that no overlap occurs on the OFDMA symbol numbers 14 among the preamble 48 a and frame control information 51 a for the sector 41 a, the preamble 48 b and frame control information 51 b for the sector 41 b, and the preamble 48 c and frame control information 51 c for the sector 41 c.

Then, the frames 47 a, 47 b and 47 c are controlled in timing such that synchronization is established among the sectors 2 a, 37 a and 41 a of the cells 1, 35 and 36 corresponding to the frame 47 a, among the sectors 2 b, 37 b and 41 b of the cells 1, 35 and 36 corresponding to the frame 47 b, and among the sectors 2 c, 37 c and 41 c of the cells 1, and 36 corresponding to the frame 47 c, and thus radio signals are transmitted and received to and from terminal stations respectively located in the sectors 2 a, 2 b, 2 c, 37 a, 37 b, 37 c, 41 a, 41 b and 41 c.

With the frames 47 a, 47 b and 47 c configured in this way, when radio signals are transmitted/received between terminal stations and the radio base-station devices 3 a, 3 b, 3 c, 38 a, 38 b, 38 c, 42 a, 42 b and 42 c, no interference occurs among the preambles 16 a, 16 b, 16 c, 47 a, 47 b, 47 c, 48 a, 48 b and 48 c and the frame control information 49 a, 49 b, 49 c, 50 a, 50 b, 50 c, 51 a, 51 b and 51 c, and the frame transmission efficiency is improved not only between sectors but also between cells.

Sixth Preferred Embodiment

In the fifth preferred embodiment, no overlap occurs on the OFDMA symbol numbers 14 among the preambles 16 a, 16 b and 16 c and frame control information 49 a, 49 b and 49 c of the frames 47 a, 47 b and 47 c corresponding to the sectors 2 a, 2 b and 2 c of the cell 1, the preambles 47 a, 47 b and 47 c and frame control information 50 a, 50 b and 50 c of the frames 47 a, 47 b and 47 c corresponding to the sectors 37 a, 37 b and 37 c of the cell 35, and the preambles 48 a, 48 b and 48 c and frame control information 51 a, 51 b and 51 c of the frames 47 a, 47 b and 47 c corresponding to the sectors 41 a, 41 b and 41 c of the cell 36; however, as shown with the OFDMA frame structure illustrated in FIG. 10, the preambles of the frames 47 a, 47 b and 47 c may be made of different patterns of preambles 60 a, 60 b, 60 c, 61 a, 61 b, 61 c, 62 a, 62 b and 62 c that have no correlation with each other, i.e. that can be detected even when interference occurs between preambles, and they may overlap each other on the OFDMA symbol numbers 14. The reference characters 63 a, 63 b, 63 c, 63 d, 64 a, 64 b, 64 c, 64 d, 65 a, 65 b, 65 c and 65 d indicate NULL subcarrier regions. In FIG. 10, the same reference characters as those used in the fifth preferred embodiment indicate the same or corresponding components and so they are not described again here.

In this way, the preambles 60 a, 60 b, 60 c, 61 a, 61 b, 61 c, 62 a, 62 b and 62 c of different patterns having no correlation with each other overlap each other on the OFDMA symbol numbers 14, and thus the overhead is reduced for the time of the overlap of preambles 60 a, 60 b, 60 c, 61 a, 61 b, 61 c, 62 a, 62 b and 62 c, and the frame transmission efficiency is further improved than in the fifth preferred embodiment.

Seventh Preferred Embodiment

In the sixth preferred embodiment, there are overlaps on the OFDMA symbol numbers 14 among the preambles 60 a, 60 b and 60 c of the frames 47 a, 47 b and 47 c corresponding to the sectors 2 a, 2 b and 2 c of the cell 1, the preambles 61 a, 61 b and 61 c of the frames 47 a, 47 b and 47 c corresponding to the sectors 37 a, 37 b and 37 c of the cell 35, and the preambles 62 a, 62 b and 62 c of the frames 47 a, 47 b and 47 c corresponding to the sectors 41 a, 41 b and 41 c of the cell 36; however, as shown with the OFDMA frame structure illustrated in FIG. 11, in addition to arranging the preambles 60 a, 60 b, 60 c, 61 a, 61 b, 61 c, 62 a, 62 b and 62 c to overlap each other on the OFDMA symbol numbers 14, the frames may be configured such that the pieces of frame control information 70 a, 70 b and 70 c of the frames 47 a, 47 b and 47 c corresponding to the sectors 2 a, 2 b and 2 c of the cell 1 do not overlap on the logical subchannel numbers 13 a, 13 b and 13 c, such that the pieces of frame control information 71 a, 71 b and 71 c of the frames 47 a, 47 b and 47 c corresponding to the sectors 37 a, 37 b and 37 c of the cell 35 do not overlap on the logical subchannel numbers 45 a, 45 b and 45 c, and such that the pieces of frame control information 72 a, 72 b and 72 c of the frames 47 a, 47 b and 47 c corresponding to the sectors 41 a, 41 b and 41 c of the cell 36 do not overlap on the logical subchannel numbers 46 a, 46 b and 46 c. The reference characters 73 a, 73 b, 73 c, 73 d, 74 a, 74 b, 74 c, 74 d, 75 a, 75 b, 75 c and 75 d indicate NULL subcarrier regions. In FIG. 11, the same reference characters as those used in the fifth and sixth preferred embodiments indicate the same or corresponding components and so they are not described again here.

In this way, the pieces of frame control information 70 a, 70 b and 70 c are arranged such that they do not overlap on the logical subchannel numbers 13 a, 13 b and 13 c, the pieces of frame control information 71 a, 71 b and 71 c are arranged such that they do not overlap on the logical subchannel numbers 45 a, 45 b and 45 c, and the pieces of frame control information 72 a, 72 b and 72 c are arranged such that they do not overlap on the logical subchannel numbers 46 a, 46 b and 46 c, and then the pieces of frame control information 70 a, 70 b, 70 c, 71 a, 71 b, 71 c, 72 a, 72 b and 72 c can overlap on the OFDMA symbol numbers 14, and then the overhead is reduced for the time of the overlap, and the frame transmission efficiency is further improved than in the sixth preferred embodiment.

The fifth to seventh preferred embodiments have shown a configuration using three cells, but this configuration is only illustrative and not restrictive, and not intended to particularly limit the number.

Eighth Preferred Embodiment

As shown in the network configuration diagram of FIG. 12, the radio base-station apparatuses shown in the first to seventh preferred embodiments are connected through a network 80 to a monitoring control apparatus 82 that performs management, setting, and changing of the structure of frames respectively formed in the plurality of radio base-station devices 81, and that also performs management, setting, and changing of the offsets added to the frames. This enables efficient centralized operation of the radio base-station apparatuses. The plurality of radio base-station devices 81 correspond to the radio base-station devices 3 a, 3 b, 3 c, 38 a, 38 b, 38 c, 42 a, 42 b and 42 c described in the first to seventh preferred embodiments.

Industrial Applicability

The radio base-station apparatus of the present invention is applicable to radio base-station apparatuses that transmit and receive radio signals to and from terminal stations such as mobile phones. 

What is claimed is:
 1. A radio base-station apparatus for performing OFDMA multiple-access processing in a cell divided into a plurality of sectors, comprising: a plurality of radio base-station devices, each radio base-station device associated with one of the sectors and including a physical layer processing block that forms frames with logical subchannel numbers and OFDMA symbol numbers used for transmission and reception, and a transmitter/receiver block that transmits the frames, wherein each of the radio base-station devices operates on a same radio frequency with a frequency reuse factor of 1, each of the frames includes a preamble and frame control information arranged sequentially at a beginning of the respective frame, and when each of the radio base-station devices operates on the same radio frequency with the frequency reuse factor of 1, the radio base-station devices transmit the frames such that the preambles and frame control information of the frames do not interfere with each other between the frames and that beginnings of data regions of the frames on the OFDMA symbol numbers coincide with each other.
 2. The radio base-station apparatus according to claim 1, further comprising a reference clock source that generates a reference clock to synchronize the frames formed respectively by the radio base-station devices; and a delay adder that adds an offset to the beginning of a given one of the frames synchronized on the basis of the reference clock, wherein the offset is added to the beginning of the given one of the frames such that the preambles and frame control information arranged sequentially at the beginnings of the frames formed respectively by the radio base-station devices do not overlap on the OFDMA symbol numbers.
 3. The radio base-station apparatus according to claim 2, wherein the reference clock source is a GPS receiver that receives a GPS signal from which the reference clock is extracted.
 4. The radio base-station apparatus according to claim 1, further comprising a reference clock source that generates a reference clock to synchronize the frames formed respectively by the radio base-station devices, wherein the preambles and frame control information sequentially arranged at the beginnings of the frames formed respectively by the radio base-station devices are arranged such that the preambles are transmitted together, are made of different preamble patterns having no correlation with each other, and overlap on the OFDMA symbol numbers, and the respective frame control information does not overlap on the OFDMA symbol numbers.
 5. The radio base-station apparatus according to claim 4, wherein the reference clock source is a GPS receiver that receives a GPS signal from which the reference clock is extracted.
 6. The radio base-station apparatus according to claim 1, further comprising a reference clock source that generates a reference clock to synchronize the frames formed respectively by the radio base-station devices, wherein the preambles and frame control information sequentially arranged at the beginnings of the frames formed respectively by the radio base-station devices are arranged such that the preambles are transmitted together, are made of different preamble patterns having no correlation with each other, and overlap on the OFDMA symbol numbers, and the respective frame control information does not overlap on the logical subchannel numbers and does overlap on the OFDMA symbol numbers.
 7. The radio base-station apparatus according to claim 6, wherein the reference clock source is a GPS receiver that receives a GPS signal from which the reference clock is extracted.
 8. A radio communications system, comprising: the radio base-station apparatus according to claim 2 and further including a network interface that connects to a network; and a monitoring control apparatus that connects to the network and performs management, setting, and changing of the preambles and frame control information arranged in the frames formed respectively by the radio base-station devices of the radio base-station apparatus, and the offset added to the frame.
 9. A radio communications system, comprising: a plurality of radio base-station apparatuses according to claim 3, each radio base-station apparatus associated with one of a plurality of cells, wherein the GPS receivers of the radio base-station apparatuses respectively extract the respective reference clocks from the respective GPS signals, and the radio base-station apparatuses are synchronized on the basis of the reference clocks.
 10. A radio communications system, comprising: a plurality of radio base-station apparatuses according to claim 5, each radio base-station apparatus associated with one of a plurality of cells, wherein the GPS receivers of the radio base-station apparatuses respectively extract the respective reference clocks from the respective GPS signals, and the radio base-station apparatuses are synchronized on the basis of the reference clocks.
 11. A radio communications system, comprising: a plurality of radio base-station apparatuses according to claim 7, each radio base-station apparatus associated with one of a plurality of cells, wherein the GPS receivers of the radio base-station apparatuses respectively extract the respective reference clocks from the respective GPS signals, and the radio base-station apparatuses are synchronized on the basis of the reference clocks.
 12. The radio communications system according to claim 9, wherein the radio base-station apparatuses each include a network interface that connects to a network; and a monitoring control apparatus that connects to the network and performs management, setting, and changing of the preambles and the frame control information arranged in the frames formed respectively by the radio base-station devices of the radio base-station apparatuses, and the offsets added to the frames. 